They had to study the night skies through their telescopes every Wednesday at midnight and learn the names of different stars and the movements of the planets. (describing Astronomy class in HP and the Philosopher's Stone)

Why do they study such a Muggle subject?

The only plausible guess would be for Divination, but they ALREADY have a separate Divination class (and we see when Firenze starts teaching them that the parts of Astronomy that are relevant ARE taught in Divination).

Is there some connection between astronomy and Magic outside Divination? Or is that class simply a prerequisite for Divination?

UPDATE: Just to clarify: Phases of the moon (a) don't need an astronomy class or a telescope; (b) aren't what is studied in the Astronomy class based on the quote above. So any answers based on "this ingredient depends on phase of the moon" factoids do NOT address my question at all, sorry. (now, if there was a canon ingredient based on planetary movements, that'd be a good answer)

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    At a guess, because certainly spells can only be cast and certain ingredients can only be collected when the planets and moon are in a certain state. – Valorum Nov 15 '14 at 18:24
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    Because JK "oh my dear maths" R doesn't know the difference between astronomy and astrology? – SQB Nov 15 '14 at 18:36
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    it must be part of the general romanticized "old school" décor and level of science, like the Hogwart express using coal – Reed -SE is a Fish on Dry Land Nov 15 '14 at 20:31
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    @Reed - most of the Wizarding stuff (including nearly 100% of Hogwarts - parchments, quills, cauldrons, robes etc...) dates to 16th century or so, not 19th. – DVK-on-Ahch-To Nov 15 '14 at 20:33
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    The question seems to assume that everything taught at Hogwarts is supposed to be useful in the practice of wizardry. Is there canon evidence for that? (I've only read the first book.) As far as I know, there is nothing strange or unusual about a vocational high school offering instruction in such stuff as history, literature, and music, in addition to work-oriented subjects like welding and woodworking. – user14111 Feb 1 '15 at 0:58

This is an interesting question -- I'll take a stab at answering it. Please note that I'm going to give an out-of-universe answer as a possible solution to the question regarding Astronomy in Harry Potter. J.K. Rowling studied many myths and lore, and molded her universe using aspects of these real life tropes.


It's already been established in other answers that Astronomy is compulsory at Hogwarts through year five. According to J.K. Rowling on Pottermore:

Very specialised subjects such as Alchemy are sometimes offered in the final two years, if there is sufficient demand.

Pottermore - Philosopher's Stone - Hogwarts school subjects


I looked up Alchemy on the Wikipedia:

Alchemy is the art of liberating parts of the Cosmos from temporal existence and achieving perfection which, for metals is gold, and for man, longevity, then immortality and, finally, redemption. Material perfection was sought through the action of a preparation (Philosopher's Stone for metals; Elixir of Life for humans), while spiritual ennoblement resulted from some form of inner revelation or other enlightenment (Gnosis, for example, in Hellenistic and western practices)

Wikipedia - Alchemy

It's reasonable to extrapolate that Astronomy is an essential pre-requisite for Alchemy. As Alchemy is offered on a limited basis, and students may not express their interest in Alchemy until after their fifth year, compulsory Astronomy could mitigate the chance that fifth years would suddenly express a desire to study Alchemy, yet know nothing about Astronomy or the Cosmos. Surely Dumbledore would have ensured Hogwarts' curriculum fully prepared all students for the possibility that they might study a specialized subject in years six and seven, and that means compulsory pre-requisites.


The Cosmos are essential to Alchemy. Alchemy is a legitimate Hogwarts area of study and the historical theme of Alchemy, the Philosopher's Stone, and the Elixir of Life is fully consistent with canon. Ostensibly, the possibility exists that students in Harry's year may have studied Alchemy: For example, J.K. Rowling recently revealed that Draco Malfoy has a strong interest in alchemist papers.

I see in [Draco's] hobbies further confirmation of his dual nature. The collection of Dark artefacts harks back to family history, even though he keeps them in glass cases and does not use them. However, his strange interest in alchemical manuscripts, from which he never attempts to make a Philosopher's Stone, hints at a wish for something other than wealth, perhaps even the wish to be a better man.

Pottermore - Half-Blood Prince - Draco Malfoy

Perhaps Draco, as well as other students, first cultivated an interest in Alchemy at Hogwarts. If so, Astronomy would have been essential if they actually studied it there.

  • This makes more sense than the Uranus one. – Arturo Torres Sánchez Feb 3 '15 at 20:00
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    @ArturoTorresSánchez - You've got to admit that the uranus joke makes more sense thematically. This is, after all a children's book. – Valorum Feb 3 '15 at 20:14
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    @Richard -- Nice try with the whole "children's books" thing ;) Regardless, I admit to giggling at Ron's request to Lavender too. – Slytherincess Feb 3 '15 at 20:16
  • I wonder if Ron has a fetish. ...um, I mean, a small magical charm or talisman. Yeah, that's what I meant. – KSmarts Feb 3 '15 at 20:28

Out of universe, the primary reason why Hogwarts students seem to study astronomy is to facilitate low-comedy.

‘It is Uranus, my dear,’ said Professor Trelawney, peering down at the chart.

‘Can I have a look at Uranus, too, Lavender?’ said Ron.

Additionally, the Tower of Astronomy itself provides a convenient location to allow Harry to see events unfolding but not be able to take part in them (such as the attack on Hagrid) and provides somewhere high for flight-based escapades (such as smuggling dragons out of Hogwarts) to take place.

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    Please see update on the question, I figured my comment wasn't clear enough so moved it into the question itself. "Phase of the moon" isn't something that they do, or even need, study in astronomy. – DVK-on-Ahch-To Nov 15 '14 at 20:18
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    @DVK - Hmm. I'm not sure I agree with you that studying the moon isn't astronomy but heck, it's your question. – Valorum Nov 15 '14 at 21:09
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    @dvk - In OOTP, Harry studies the moon during an astronomy test; "He could feel Professor Marchbanks’s eyes on the back of his neck and pressed his eye again to his telescope, staring up at the moon though he had marked its position an hour ago, but as Professor Marchbanks moved on he heard a roar from the distant cabin that echoed through the darkness right to the top of the Astronomy Tower.." – Valorum Nov 15 '14 at 22:19
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    @DVK Or the implication the the Moon's position wouldn't change after an hour. – KSmarts Jan 23 '15 at 18:47
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    That quote is from a Divination lesson, though. Learning Astronomy had nothing to do with it. – Anthony Grist Sep 27 '15 at 17:29

Yes, there are several connections between Astronomy and Alchemy.

It was a core belief in Alchemy that element changes were connected to the movement of the celestial bodies. They believed that phenomena of change (crystal growth, wood decay etc. etc.) all depended on outer circumstances. So to create potions or other magical substances astronomy would have been paramount to find the best way to create them.

It is now relatively unknown, but the known five planets/Moon/Sun had the following identifications with the weekdays and the elements of alchemy:

Sun Sunday Gold
Moon Monday Silver
Mars Tuesday Iron
Mercury Wednesday Mercury
Jupiter Thursday Tin
Venus Friday Copper
Saturn Saturday Lead

So the associations with the planets are extremely old. What Rowling got wrong is the idea that people could use telescopes to get a good look at celestial bodies. Even in a good telescope the planets are incredibly small and washed out, even with the best telescopes stars are always points. The moon is nice, Jupiter, Saturn and Jupiter's moon could be discerned, but they are no match to Voyager pictures.

What is really interesting (e.g. Alchemy) is the position of the celestial bodies, absolute (their position in the ecliptik) and relative (to other bodies: opposition, occultation of stars by planets etc.).

  • This is interesting stuff. Can you offer any proof from within the novels that this is the case? – Valorum Feb 1 '15 at 0:26
  • Uh, I am talking about the connection between Alchemy and Astronomy within our reality. As Rowling did her research (Hint: Nicholas Flamel is in fact an alchemist who found the philosophers stone according to legend. And the philosophers stone is in fact supposed to turn lead to gold and allow to gain immortality) I think she knew how important astronomy for alchemy is. If someone is interested, read: "Alchemy: The Philosophers Stone" from Allison Coudert. – Thorsten S. Feb 1 '15 at 11:40

Astronomy is the study of celestial objects and their nature. Muggle Astronomy includes physics and chemistry, which are not Wizarding subjects. Because Wizards are not aware of or do not learn physics and chemistry that allow them to postulate based on those sciences, they're left with making direct observations.

In this case, it means that Wizards observe stars and their positions. This would be considered observational astronomy. How they move, what color they are, what other bodies are near them, etc., are all quantifiable properties. Similar early astronomical recordings in the Muggle-verse were precursors to the modern astronomy we know.

Being able to observe and identify celestial bodies would indeed be important to Wizards and Witches who needed to gather ingredients or perform spells under certain astrological conditions. If you don't know how to predict the movement of a star, how do you then plan on performing an act when the star is in a specific place? How do you use stars to navigate if you don't know how to organize and identify them?

In fact, Hogwarts students are shown to need to develop start charts, in their 3rd years and also for the OWLs. Star charts are associated with astronomy, even if they may also be used for Astrology.

We are also made aware that Hogwarts distinguishes between Astronomy and Astrology by this exchange between Pavarti and Firenze:

Parvati Patil: "Professor Trelawney did astrology with us! Mars causes accidents and burns and things like that, and when it makes an angle to Saturn, like now — that means people need to be extra careful when handling hot things—"
Firenze: "That is human nonsense. Trivial hurts, tiny human accidents, these are of no more significance than the scurryings of ants to the wide universe, and are unaffected by planetary movements."

Here it's explained that Astrology is indeed taught at Hogwarts, under the purview of Divination. The curriculum of Astronomy is likely helpful for students that opt to take Divination, especially during the Astrology portions of the class. Concepts and taught in Astronomy (observation, classification, identification, predictions) could also be of value to other Hogwarts electives, such as Arithmancy. Or, life in general.

As for a canon reason for needing to know astronomy, specifically phases of the moon, we have to look no further than Werewolves. They transform under a full moon. Knowing when a full moon will occur (regardless of where you're at in the world) will be of import to anyone dealing with lycanthropes. It's also necessary for anyone wanting to harvest some Mooncalf dung.

Lastly, Hogwarts is the primary source of all education for its attending students. Thus, it makes sense that they would want to teach some skills that aren't necessarily directly related to the casting of spells or making potions. Astronomy provides a way for them to teach learning skills. If a student can make a complicated star chart based on observations, then perhaps later in life they can apply those skills to their other pursuits. A great example of a Wizarding achievement that would use some of these basic skills is Dumbledore's study and categorization of the twelve uses of dragon's blood.


Besides Astronomy, Hogwarts also has other classes which seem to be pure theoretical stuff.

They also learn arithmancy, which is described as numerology / making predictions based on charts (pity the teachers name isnt prof Harry Sheldon) Hermione says it's her favourite subject so it's probably not humbug like astrology/divination. There's also ancient runes which seems to be an ancient language, so why not astronomy? Prof Sinistra teaches them about the moons of Jupiter and the like

"... you must have misheard Professor Sinistra, Europa's covered in ice, not mice."

(OP) Which is curious stuff if it was known to wizards for a while and not just copied from muggle textbooks.

Update: (It seems arithmancy is required for curse-breaking, so it's also practical knowledge)

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    ancient runes seems to have clear practical application in a typical magical world (not explicitly in-canon in Potterverse however). Ditty arithmancy - think of it as magic's equivalent of learning calculus for Muggle engineers and scientists. – DVK-on-Ahch-To Jul 16 '16 at 16:33

I have not found any "real point" of studying Astronomy for future reasons, for instance, a job, except for an obvious one which I will explain later. However i have found some information that somewhat answers your question.

The first point is that it was a core subject taught as Hogwarts. This is found on Harry Potter Wiki,

"Astronomy is a core class and subject taught at Hogwarts School of Witchcraft and Wizardry."

The point is that they had to do it. The quote can be found here, first line.

A core class, in case you didn't know is, quote on quote,

"a set of common courses required of all undergraduates and considered the necessary general education for students, irrespective of their choice in major."

Other points that are similar, are that,

"students must study the night skies through their telescopes every Wednesday at midnight and learn the different names of the stars and the movements of the planets."

They "must study" the subject, probably without a choice. Quote found here, under Curriculum, First Year, first line.

Again, another similar point is,

"During the fifth year of studies at Hogwarts, students must study Jupiter's moons and write an essay containing facts such as Europa being covered by ice and Io having many volcanoes"

Again, they "must study", most likely without of choice. Quote found here, under Curriculum, Fifth Year, first line.

And finally, best for last and the most obvious. You would need to know everything about Astronony, if you wanted to teach it! Other professors would probably need to know a small bit of it, just because it may have been on a test, to qualify to become a professor.

I could not find any other purposes, however it is know that to become an Auror, you are recommended (by Minerva) that Defence Against the Dark Arts, Transfiguration, Charms, and Potions would be useful N.E.W.T. level classes for those wishing to pursue a career as an Auror. Note that other skills are required for jobs, this may be the case that Astronomy might be required for other jobs.

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    None of these quotes explain how astronomy might be useful to you as an ordinary wizard/witch. – Valorum Nov 15 '14 at 23:08
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    FYI: Wikia is not canon (especially Harry Potter Wikia). It's just stuff someone wrote on Internet, some correct, some not, some just narrative made up to explain canon in nice and not-always-accurate words. In this specific case, it is flat out wrong - there's no "core" subjects at Hogwarts in canon at all - the term was made up by whoever wrote that page. All the bolded "must" words are also made up, basically to explain the basic fact that you as a student have to study what your classes teach you. – DVK-on-Ahch-To Nov 15 '14 at 23:27
  • You should never rely in Wikia, especially when you base the answer on interpreting specific words in Wikia page that don't come from canon (as in, you have a canon quote with those words). – DVK-on-Ahch-To Nov 15 '14 at 23:29
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    Moreover, this answer isn't even correctly answering the question even leaving aside sourcing: Basically, you're answering the question of "why is there a required class" with "because it's a required class". – DVK-on-Ahch-To Nov 15 '14 at 23:31
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    The question asked, "What's the point of studying Astronomy at Hogwarts?" I answered by saying it was required. – Jake Nov 16 '14 at 0:54

Maybe it is a peperation for having the wizard and witches learn about astronomy outside of our own solar system. Something that muggles can't do but they can.

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    Can you offer any evidence that wizards have greater (or indeed any) additional knowledge of extra-solar stuff? – Valorum Nov 27 '15 at 13:57
  • More to the point, Muggles can indeed study extrasolar objects. This arguably constitutes the bulk of astronomy. – Adamant Jul 17 '16 at 5:12

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